Once you unlock password mode ,go to bonus and select password then type...
You get a new mamodo, and man she can pack a punch!
Beat tia's story after beating zatch's story to get password.
This is how to unlock all the power-up characters in the NA version. For the characters in story mode, it is easier if you have finished that specific character's story first and then go back. If the character doesn't appear the first time, do something else(Time Attack, Bonus Mode, etc.) and come back and try again. To unlock the characters that are in Story mode, you must beat them in battle.